In the past, several different methods and techniques have been used to cut glass sheets. The most widely used method is mechanical scoring using a wheel made of a hard material and breaking the glass along the score line. The mechanical scribing and breaking process generates debris that collects on the glass surface and requires thorough cleaning. Therefore, glass technology areas that require high glass quality, such as the LCD industry, cannot reliably use mechanical scribing techniques to form glass sheets.
Other widely used methods include the use of lasers to score and/or separate glass sheets. In one technique, a laser beam is used to score the glass; the glass is then separated by mechanical separation techniques. When the laser beam is moved across the glass sheet, it creates a temperature gradient on the surface of the glass sheet, which is enhanced by a coolant (such as a gas or liquid) that follows the laser beam at some distance. Specifically the heating of the glass sheet by the laser and the rapid cooling of the glass sheet by the coolant creates tensile stresses in the glass sheet. The tensile stresses create a crack (or score vent) in the glass surface. In this manner, a score line is created along the glass sheet. The glass sheet can then be separated into two smaller sheets by separating the glass sheet along the score line. Yet another technique uses a first laser beam to score the glass. A second laser beam of a different configuration is used to accomplish laser separation.
Conventional techniques for laser scoring and separating result in limited exposure (or residence) time on the glass sheet provided due to the use of a relatively short laser beam. Slow scoring or separating speeds are needed to achieve the required exposure time of the laser beam on the glass sheet, but result in inefficient glass sheet separations. At high cutting speeds, the exposure time can be insufficient to heat the glass to the required temperature, unless a higher power density beam is used. However, higher power density laser beams can cause overheating of the glass and, as a consequence, create significant residual stress issues in the glass sheet. In order to solve these problems, long, single laser beams have been used, which provide extended residence time and are thus capable of adequately separating glass sheets at a higher scoring or separating speeds. However, due to the elongation of the laser beams necessary to achieve higher speeds, these techniques are limited to linear scoring trajectories.
In order to separate glass sheets along curved trajectories, the single laser beam can be shortened, which brings back the issue of limited residence time and slow cutting speed. Other techniques to achieve separation along non-linear trajectories have required continuous reshaping of the laser beam as it is guided along the non-linear trajectory, which requires high levels of precision and can result in highly complex and potentially inefficient systems.
Thus, there is a need in the art for systems and methods to cut glass sheets along varying trajectories that include linear and/or non-linear portions.